One of nine youth team players who signed an 18 month professional contract in February 2008, Morrison was one of only two to make their senior debuts before the season was out, when injury to Jerel Ifil handed him a chance as a first half substitute in a 1-1 draw at Gillingham in April. Morrison had been named as "Apprentice of the Month" out of all the league clubs the previous month - and May began with Morrison making his full debut in the final game of the season, giving an assured display against Millwall - it was soon revealed that both Everton and Sunderland were already known to be admirers of the youngster.

Injury to Jerel Ifil handed Morrison another chance early the following season, when he was given a starting place for the visit of Q.P.R. in the Carling Cup, and a match at Cheltenham the following week. Morrison dropped out of the squad when Ifil returned to action, until an awful display by Ifil against Leeds in mid-September prompted manager Maurice Malpas to drop him - and Morrison kept his place in the side right through until November. He netted his first senior goal with an assured finish against Oldham in October, prompting Malpas to praise the young defender - but after Malpas was sacked the following month, caretaker boss Byrne dropped Morrison from the squad, and allowed him to return to his hometown of Plymouth to recharge his batteries and prevent him from burning out. Soon after, it was revealed that Swindon had refused offers from higher level clubs to take Morrison on trial.

When new boss Danny Wilson arrived in December, he stated that defence was an area where he felt experience was needed, especially with the Town in relegation trouble - and though Morrison had returned to the bench in recent weeks, he dropped out of the squad completely after the arrival of Gordon Greer on loan from Doncaster. It was February before Morrison returned to the squad, and he regained his starting place back at the beginning of March, after Wilson had declared him as being the "future of the club", an offering him a one-year contract extension. Morrison remained in the side for the whole month, before a knee injury sustained in a relegation clash with Yeovil prematurely ended his season. Nonetheless, Morrison was named as the club's Young Player of the Year, and over the summer, speculation about his future intensified, as Celtic were rumoured to have enquired about a £1.25 million double deal involving both Morrison and Simon Cox, which was later denied.

The 2009/10 season proved to be a frustrating one for Morrison though. He started the season in the first eleven, and stayed in the side until the end of August - scoring the winner in a 1-0 victory over Southampton - before being rested for the Carling Cup tie at Wolves, where captain Greer and new signing Scott Cuthbert held the Premier League side to a scoreless draw. Morrison then found himself benched seemingly for good - making just one start in a 1-1 draw at Walsall with Greer injured - and he was surprisingly allowed to join Southend on a loan deal in November. He didnít make the best start - getting sent off on his debut against Yeovil - when he returned to the County Ground in January, it was another month before he got any game time, replacing Greer again after he picked up another injury. His final appearance of the season came in March, when he started in a 2-1 defeat at MK Dons - making an awful error to gift the home side a lead after just two minutes of the game, and being substituted just before the hour - after that, he found himself behind Lecsinel Jean-Francois in the pecking order, and he only made the eighteen twice more without being used.

When Greer departed over the summer to join Brighton, manager Wilson stated that they were looking to Morrison to fill his place that season - so it was somewhat of a surprise when he started the season on the bench, with Jean-FranÁois preferred in defence again. After a poor start to the season though, Morrison soon found himself in the side - and though the Town were obviously missing Greer's experience at the back, Morrison himself gave some decent performances, and also proved dangerous from set pieces - scoring four goals in a ten game spell between the end of September and beginning of November.

During a weather-hit December though, after Swindon had been knocked out of the cup by non-league Crawley, Wilson decided to change three of his back four over the Christmas period, and Morrison was one of those dropped to the bench - but he was soon recalled after a home defeat against Bournemouth on New Years' Day, for a televised clash at Charlton - the game proved to be Swindon's best performance of the whole season, with Morrison notching another headed goal. That proved to be his last strike for the Town though - ten days later, and just after the defender's twentieth birthday, Championship club Reading triggered a release clause in his contract with a £250,000 bid - Morrison making the move despite chairman Andrew Fitton's advice that it wasn't necessarily the right move for him at the time.